[MWForum] when to use turtle backpacks

[Wendy Petti]

I would like to add a few more thoughts to the discussion of when to put
procedures in a backpack or in the public Procedures tab.

1) Yes, it's great to be able to "give each turtle its own DNA," as Jeff
says.  If you have no need for individual turtle behaviors, then it makes
sense to use the public procedures tab.  But one of the fun things about MW
EX is the opportunity for customizing turtles, and I hope we'll encourage
students to think creatively about the possibilities.  (For instance, give
each turtle its own commands for a "dance" procedure and then create a
button:  everyone [dance] and watch each turtle move in a different way.
Think of things to be gained when turtles are exported to other projects...
such as when each student designs a turtle and then these turtles gather on
one page to interact.)

2) If we're going to get the most out of MW EX, we should be encouraging
students to use the features of all six tabs of the backpack rather than
discouraging the use of backpacks.

3) Remember that a backpack can be left open and dragged aside (away from
the project page); open backpacks do slow the turtle's movements, but while
you're editing procedures, it shouldn't be a big deal to leave the backpacks
open.

4) Also remember to consult the Project tab.  Click on all the + symbols.
If you see that a turtle has procedures, you can double-click that word or
icon in the Project tab, and the turtle's backpack will open to its
Procedures tab.  It's true that it may not be as easy to debug as having all
procedures in one place, but at least you can see which turtles have private
procedures.

5) BUT .... !!!!  I must warn you of a danger of putting procedures in a
turtle's backpack.  You can't tell by looking at a turtle if it's got
procedures or not, and if you accidentally delete a turtle, you've lost the
procedures it was carrying, and there is no way to undo this action.  This
happened to me once:  I thought I was deleting a superfluous turtle but I
was deleting an essential "loaded" turtle instead.  We are accustomed to
thinking of turtles as dispensable - easy to hatch and easy to cut.  We
aren't accustomed to thinking about their precious cargo.  Of course we need
to remind students to resave their work often (even as often as every few
minutes), but in my case I had resaved before I realized my error.  I
suggest that you change the appearance of any turtle carrying procedures, to
help prevent this mistake.  (You could change its size or color or shape.)

Wendy

Wendy Petti
OWL's MicroWorlds in Action
http://mia.openworldlearning.org
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